Dual-voltage automatic-switching electric lamp having a two-position thermal switch disposed within the envelope



Aug. 11, 1970 J. E. BLAIR 3,524,100

DUAL-VOLTAGE AUTOMATIC-SWITCHING ELECTRIC LAMP HAVING A TWO-POSITION THERMAL SWITCH DISPOSED WITHIN THE ENVELOPE 7 Filed May 20, 1968 mvempa JOHNNY E; BLAIR ATTORN evs United States Patent 01 fice 3,524,100 Patented Aug. 11, 1970 3,524,100 DUAL-VOLTAGE AUTOMATIC-SWITCHING ELEC- TRIC LAMP HAVING A TWO-POSITION THER- SWITCH DISPOSED WITHIN THE ENVE- Johnny E. Blair, Box 3, Van, W. Va. 25206 Filed May 20, 1968, Ser. No. 730,407 Int. Cl. H013 7/44, 19/78 US. Cl. 315-73 8 Claims ABSTRACT OF THE DISCLOSURE This electric lamp is started with low voltage starting current and automatically switched to higher voltage operacting current by a signal-pole double-throw thermostaticswitch positioned inside the lamp bulb adjacent the filament so as to receive heat therefrom. This thermostatic switch is normally closed on a contact in a low voltage starting current circuit containing a normally-open start switch which when closed, initially energizes the filament with low voltage starting current sufliciently to heat the thermostatic switch element adequately to cause it to open the starting current circuit and to close a higher voltage operating current circuit containing a normallyclosed stop switch. The stop switch when opened, deenergizes the filament so that it ceases to momentarily emit heat, whereupon the thermostatic switch element shifts back to close on its starting voltage contact, ready to re-energize the filament when the normally open start switch is again closed. The starting current may conveniently be of much lower voltage, such as 25 volts, than the voltage of the operating current which is usually 110 volts, thereby enhancing safety and increasing the operating life of the lower-voltage switch contacts. Momentary-contact switches, such as pushbutton switches, may conveniently be used.

The drawing shows a dual-voltage automatic-switching electric lamp, according to one form of the invention.

Referring to the drawing in detail, there is shown a dual-voltage automatically-switching incandescent-filament electric lamp, generally designated 10, as normally connected to a ground line 12 and also normally connected to a low-voltage starting current circuit 14 containing a normally-open start switch 16. The closing of the start switch 16 energizes the starting line 14 and automatically causes the electric lamp to be switched over to and become energized from an operating circuit 18 containing a normally-closed stop switch 20. The low- I voltage starting current circuit 14 includes a line 22 running from the start switch 16 to the electric lamp 10 and also includes a line 24 running from the start switch 16 as Well as a ground branch line 26. The starting current circuit 14 is connected to a source of low-voltage starting current (not shown). The operating circuit 18 inches a ground branch line 30 from the ground line 12 and also includes a line 28 connecting the lower fixed contact support 56 of the electric lamp 10 to one side of the normally-closed stop switch 20, whence a line 32, along with the ground branch line 30, is connected to a source of higher voltage operating current. Such starting current may have a potential of 25 volts, whereas such operating current may have a potential of 110 volts. As shown in the drawing, the start switch 16 is spring-pressed into a normally-open position whereas the stop switch is spring-pressed into a normally closed position.

The dual-voltage automatically-switching incandescentfilament electric lamp 10 includes a metallic base 34 of any suitable type, such as the so-called Edison screw-type base commonly in use in the United States or the so-called Ediswan base of the bayonet type commonly in use in England and other European countries. The base 34 ordinarily is inserted in a conventional socket (not shown) of a corresponding type, which socket has contacts engaged by correspondingly-located contacts in the base 34. For purposes of simplification, the socket is omitted and the connections to the interior of the lamp 10 are shown as made directly with the control and operating circuits 14 and 18 respectively through a central insulated portion 36 rather than through a conventional base with its conventional metallic side and central portions insulated from one another.

Secured to the base 34 is a translucent envelope or lamp bulb 40 constructed of glass with an external bulb portion 42 joined to a reversely-directed upstanding hollow stem 44. The interior chamber 46 of the bulb 40 is preferably either evacuated or filled with an inert gas, such as nitrogen or argon. Seated in the insulated portion 36 and extending through the top of the hollow stem 44 in sealed engagement therewith are two oppositelybent metallic filament supports 48 and 50 respectively, to the opposite upper ends of which are joined the opposite ends of an electric light filament 52, preferably of tungsten. Also seated in the insulated portion 36 and hollow stem 44 are the upper and lower fixed contact supports 54 and 56 for the upper and lower fixed contacts 58 and 60 respectively of a thermostatic switch, generally designated 62, havin ga movable bimetallic switch blade of element 64 fixedly mounted at 66 on the left-hand filament support 48. The bimetallic switch blade or element 64 is composed of two strips of dissimilar metals having different coefficients of thermal expansion such that when heated,'the differential expansion there between causes the switch blade 64 to shift with a snap action from engagement of its contact 68 With the upper fixed contact 58 to engagement with the lower fixed contact 60, in the manner described below in connection with the operation of the invention.

From the drawing it will be seen that the right-hand filament support 50 is connected to the ground circuit 12 at the junction of its branches 26 and 30, whereas the left-hand filament support 48 is connected at 66 to the thermostatic switch blade 64. The upper and lower contact supports 54 and 56 of the thermostatic switch 62 are connected respectively to the lines 22 and 28 of the startnig circuit 14 and operating circuit 18 leading to the normally-open and normally-closed momentary contact start and stop switches 16 and 20 respectively.

In the operation of the invention, let it be assumed that the lines 24 and 26 of the starting circuit 14 are connected to a source of starting current, usually low-voltage, and that the lines 30 and 32 of the operating circuit 18 are connected to a source of operating current, usually at a considerably higher voltage than the starting circuit volt age. If it is desired to light the incandescent lamp 10, the operator depresses the normally-open momentary contact start switch 16, thereby closing the circuit to the filament 52 through the lines 24 and 22, the upper switch contact support 54, the upper switch contact 58, the thermostatic switch blade 64, the filament support 48, the filament 52, the filament support 50 and the line 26.

The resulting flow of starting current through the filament 52 radiates sufiicient heat to the thermostatic switch 62 to cause the metallic components of the bimetallic switch element 64 to expand differentially and bend the switch element 64 so as to disengage its movable contact 68 from the upper fixed contact 58 and engage it with the lower fixed contact 60. This action disconnects the filament 52 from the starting circuit 14, even though the momentary contact start switch 16 has not been released by the operator, and connects the filament 52 to the operating circuit 18 by way of the lines 32 and 28, the nor- 3 mally-closed momentary contact stop switch 20, the lower contact support 56, the thermostatic switch blade 64, the filaments 48 and 50, and the line 30.

The filament 52 continues to glow at maximum brilliance while thus energized by operating voltage current until the operator decides to switch off the lamp 10. This he does by Opening the normally-closed stop switch 20, consequently de-energizing the filament 52, causing it to cease emitting heat, whereupon the thermostatic switch blade 64 snaps back to its uppermost position shown in the drawing, re-engaging its movable contact 68 with the fixed upper contact 58 of the thermostatic switch 62. This action conditions the filament 52 for subsequent energization from the starting voltage circuit 14 when the operator next closes the start switch 16.

In actual practice, for convenience of making electric connections between the lamp base 34 and a suitable conventional lamp socket (not shown), the conductors 50, 54 and 56 are connected respectively to lamp base contacts shown diagrammatically at 70, 72 and 74. It will be understood that these contacts actually engage corresponding aligned contacts in the lamp socket rather than being directly connected to the lines 12, 22 and 28 respectively, as shown for purposes of simplification in the drawing.

The use of the electric lamp of this invention also greatly simplifies certain electric circuits presently requiring large numbers of relays and rotary controllers, such as in electric sign circuits employing several blocks of conventional electric lamps, and requiring a controller for each block of conventional lamps to form the various letters or numerals required of the sign. Thus, fifty blocks of lamps in such a prior sign required fifty rotary controllers, together with many relays. By the use of the electric lamps 10 of the present invention, only a single rotary controller is required, with the control circuit for each block of lamps 10 connected to one of the contacts on the rotary controller drum, and eliminating the prior relays. In such an installation of the lamps 10, the control current may be of the same voltage as the operating current. By this arrangement, using the lamps 10 of the present invention, a single rotary controller will cause the illumination of any letter on any one of fifty blocks of bulbs, where fifty such controllers are presently required.

I claim:

1. A dual-voltage automatic-switching electric lamp, comprising a lamp base,

a translucent lamp bulb mounted on said lamp base,

first and second electrically-conducting filament supports mounted in spaced insulated relationship within said bulb,

an electric lamp filament connected between said supports,

a first base contact mounted on said lamp base and electrically connected to said first filament support,

a thermostatic switch disposed within said bulb and including a thermally-responsive movable switch element connected to said second filament support and first and second fixed switch contacts disposed in spaced relationship with one another adjacent said movable switch element,

a low-voltage second base contact mounted on said lamp base and electrically connected to said first fixed switch contact, and

a higher-voltage third base contact mounted on said lamp base and electrically connected to said second fixed switch contact,

said movable switch element being normally engaged with said first fixed switch contact in the unenergized condition of said filament and responsive to the energization of said first and second base contacts for moving into engagement with said second fixed switch contact.

2. A dual-voltage automatic-switching electric lamp, according to claim 1, wherein said switch element is a bimetallic switch blade composed of metals of different thermal coefficients of expansion.

3. A dual-voltage automatic-switching electric lamp, according to claim 1, wherein said bulb has a reverselydirected hollow stem therein, and wherein said filament supports are mounted on said stem.

4. A dual-voltage automatic-switching electric lamp, according to claim 3, wherein fixed contact supports are mounted on said stem, and wherein said fixed contacts are mounted on said fixed contact supports.

5. A dual-voltage automatic-switching electric lamp, according to claim 4, wherein said thermally-moved switch element has a free end projecting into the space between said fixed contacts.

6. A dual-voltage automatic-switching electric lamp, according to claim 1, wherein a starting voltage electric circuit containing a normally-open momentary-contact start switch is connected to said first and second base contacts, and

wherein an operating voltage electric circuit containing a normally-closed momentary-contact stop switch is connected to said first and third base contacts.

7. A dual-voltage automatic-switching electric lamp, according to claim 6, wherein said start switch is a normally-open push-button switch.

8. A dual-voltage automatic-switching electric lamp, according to claim 6, wherein said stop switch is a normally-closed push-button switch.

References Cited UNITED STATES PATENTS 2,044,256 6/1936 Nothstine 315-73 X 3,151,263 9/1964 Jolly 3l574 X FOREIGN PATENTS 532,207 10/1954 Belgium.

JAMES W. LAWRENCE, Primary Examiner E. R. LA ROCHE, Assistant Examiner US. Cl. X.R. 3l586 

